Transparent glass-ceramic materials with a low thermal expansion coefficient (CTE), which contain a solid solution of β-quartz as the principal crystalline phase, have been described in a number of publications, in particular by W. Hoeland and G. Beall, in “Glass-ceramic technology”, Am. Ceram. Soc., Westerville (2002), pages 88-96. Said glass-ceramic materials are generally obtained by heat treating a precursor glass (more conventionally a mixture of the constituents of said glass: a mineral charge, a precursor of such glass), the composition of which is of the LiO2—Al2O3—SiO2 (LAS) type. Said heat treatment includes a nucleation stage followed by a crystal growth stage.
The manufacture of articles made of β-quartz glass-ceramic conventionally includes the three principal successive steps: a first step of melting a batch, such as a mixture of raw starting materials and/or glass cullet, usually carried out between 1550° C. to 1750° C.; a second step of cooling and forming the molten glass obtained into desired shape; and a third step of crystallizing or ceramming the shaped cooled glass by a suitable heat treatment (including the phases of nucleation and crystal growth mentioned above).
Glass-ceramic materials comprising β-quartz solid solution as the predominant crystalline phase, having various degrees of transparency and being essentially colorless, were known. For example, U.S. Pat. Nos. 4,438,210; 5,591,682; 6,677,046; United States Patent Application Publication No. 2004/0198579; GB 2 159 154; EP 0 437 228; JP 2001-348250; DE 199 39 787 and WO 02 162 79; DE 101 10 225; and DE 199 07 038, are all concerned with transparent glass-ceramic materials.
Nonetheless, current commercial products of essentially transparent, essentially colorless glass-ceramic tend to have an undesirable color tint in the visible spectrum. There remains a need of a transparent, colorless glass-ceramic comprising β-quartz solid solution as the predominant crystalline phase.